The present invention relates to a cable detecting system in which a submarine cable buried in a sea bottom is detected and repaired.
When there is something wrong with a cable buried in the bottom of the sea or a lake or a river, it must be raised to a cable ship for repair. Since a cable is buried in the sea bottom, a hook with an arm which can dredge the sea bottom is pulled by a cable ship in the approximate perpendicular direction to the cable, and said hook can detect the presence of a cable and raise the detected cable to a cable ship. In this case an operator on a cable ship monitors the tension of a rope for pulling said hook, and by the increase of tension he can recognize that the hook has engaged a cable, then the operator stops the cable ship and raises the cable by winding up the hook. However, since a cable is buried in the sand or the mud in the sea bottom, the hook sometimes breaks the cable unless the cable ship is promptly stopped just when the hook detects the cable, and in this case the cable cannot be raised. In order to solve this problem, in a prior art, a cable ship moves very slowly towing the hook and when the hook detects the cable, the towing is promptly stopped.
However, since a cable ship has high inertia, it can not stop promptly just when the hook detects a cable, and there has been just possibility of breaking the cable when engaged by the hook. Further, the tension change when the hook detects the cable is difficult to discriminate from the change of tension when the property of the and/or sand in the sea bottom varies. Accordingly, it has been very difficult to detect and raise a buried cable, and the improvement has been desired.